“Matt is resting,” Harbaugh said Friday. “He had some back spasms, too. It’s probably both me and Matt. Matt has had the back spasms, but I am going to probably slow him down a little bit more, especially this week, and then maybe next week after the game, we will get him back a little bit more.”

Birk, the 36-year-old center who is in the midst of his 15th training camp in the NFL, is listed first on the team’s depth chart, but had been plagued by health issues. Birk has been bothered by neck, elbow and knee injuries in three seasons with the Ravens, but has not missed a game.

In 2010, he played despite a swollen knee that had to be drained at least once a week. He sat out a good portion of last year’s preseason after undergoing surgery on his left knee. Birk was absent from a few minicamps this past offseason after undergoing surgery to repair varicose veins in his legs. He said the procedure could help him avoid losing strength in his leg during a rigorous 16-game schedule.